Dozens of flights from South Florida, New York and Europe to the Dominican Republic were delayed or canceled Wednesday, after air traffic controllers in the Caribbean nation were locked out in a union dispute.

The Dominican government installed military controllers, who allowed only one plane per half hour to land in the country's capital of Santo Domingo. Normally, 20 to 40 planes per hour arrive, officials said. Smaller airports were shut down, including in Punta Cana.

"It has slowed us down quite a bit," said Minette Velez, spokeswoman for American Airlines.

The airline, the largest U.S. carrier to the Dominican Republic, canceled six flights to the island nation, including two out of Miami and four out of San Juan, operated by its regional partner, American Eagle, Velez said. Several other flights were "running a bit late," she said.

In all, more than 40 flights from Miami, New York, Puerto Rico, Boston, Panama, Haiti, Venezuela, Spain, France and other European nations were either canceled or delayed, Dominican government officials said.

The slowdown put a strain on U.S. air traffic controllers, particularly those in the Miami Center radar complex, which monitors planes as they fly over South Florida toward the Caribbean, according to the U.S. National Air Traffic Controllers Association.

For five hours on Wednesday, the Miami Center held 20 flights on the ground. It had to add spacing between planes heading to the region, resulting in "serious safety concerns," said Doug Church, NATCA spokesman.

"It caused a ripple effect," he said. "Miami Center had to deal with more traffic."

Dominican air traffic controllers, seeking a salary increase and improved working conditions, had hoped for a contract settlement. Instead, the government replaced them with Air Force controllers at about 8 a.m. on Wednesday, officials said.

The NATCA condemned the lockout of civilian controllers.

"The actions of the government in the Dominican Republic are, at best, reckless," NATCA Executive Vice President Ruth Marlin said. "Not only is the government refusing to negotiate working conditions with its controllers, it has put the safety of its air traffic control system in jeopardy."

I know it was just somebody's proposal, but SDQ as a hub for any airline would be disaster. With fairly regular frequency, AA flights arriving into SDQ at night have to either circle or divert because the runway lighting suddently shuts down. The reliability of that airport is too poor for any type of hub. I think the ops that are there now tax the system. But I still love the country.

The views expressed are mine alone and do not necessarily reflect my employer’s views.